The present invention relates generally to fluid pressure detecting or measuring arrangements, and more particularly to arrangements of this type in which the fluid whose pressure is being measured is isolated from the pressure-detecting mechanism or gauge.
There are already known various constructions of fluid-pressure detecting or measuring arrangements, among them such in which a flexible member or diaphragm isolates or separates the fluid whose pressure is to be detected from the pressure-detecting mechanism or gauge proper, and wherein a pressure-transmitting fluid is used to transmit the pressure which acts on the flexible member to the gauge. In one such arrangement which is commercially available, a generally annular housing is interposed between two flanges of a pipeline and connected thereto, the inner diameter of the housing exceeding that of the pipeline. Then, an annular flexible element having an inner diameter substantially corresponding to that of the pipeline is received in the housing. This element includes a tubular section and two collars or outwardly extending arms which extend along the flanges of the pipeline and bound a confining space between themselves, the tubular portion, and the internal surface of the housing. This confining space is filled with the pressure-transmitting liquid, as is a gauge which is in communication with the confining space through a portion thereof which is sealingly received in a port of the housing that opens on the internal surface of the latter.
This known arrangement works quite satisfactorily in many instances, in that the pressure of the fluid that is to be detected acts on the flexible tubular portion of the flexible element and flexes the same accordingly, thereby displacing the corresponding amount of the pressure-transmitting fluid out of the confining space and into the gauge, which is thus subjected to a pressure corresponding to that to be detected and thus indicates the same with an accuracy which is determined solely by the construction of the gauge and is inherent therein. Moreover, since the inner diameter of the flexible tubular portion of the flexible element corresponds to that of the pipeline, there is a smooth transition between the pipeline and the flexible element, thus avoiding corners in the flow path, where ingredients of the fluid whose pressure is being detected could deposit, with deleterious effects on the performance of the arrangement. Also, the flexible element separates the fluid whose pressure is to be detected from the gauge, thus protecting the latter, for instance, from attack or clogging by such fluid. Furthermore, since the flexible tubular portion flexes during the use of the arrangement, any deposits or encrustations which may develop thereon are broken up and dissociated from the flexible portion, thus not interfering with the flexing of the latter.
However, experience with the arrangement described above has shown that, as advantageous as it may be in many respects, it still can happen that the fluid being measured penetrates into the interfaces between the flexible element or the arms thereof and the flanges of the pipeline, where it can form encrustations or deposits or otherwise interfere with the proper operation of the pressure-detecting arrangement.